Lauren Conrad wanted fireworks to go off on her birthday – and we’re not talking the kind that come from the brand of drama that only former Hills co-stars Heidi Montag, 23, and Spencer Pratt, 26, can create. So she did what any smart woman would do – she didn’t invite them to her shindig at the Roosevelt Hotel Jan. 30.

“Heidi, Spencer and Audrina simply weren’t invited, but why would they be?” one partygoer tells HollywoodLife.com exclusively. “Instead, Lauren wanted to celebrate with the people she loved.”

Namely, that person is boyfriend Kyle Howard, 31. He and LC (who actually turned 24 on Feb. 1) as well as about 20 of her friends, dined at The Dakota inside the Roosevelt before her big bash inside the hotel’s penthouse. “Lauren and Kyle were laughing and enjoying themselves. He’s so sweet and attentive with her, and he so obviously wanted her to have a great night,” says our spy.

But Kyle and Lauren’s relationship wasn’t the only thing to set off sparks on her big night: her cake literally was covered in fireworks. “The cake was in the shape of a giant chocolate-ycupcake with real live sparklers! It was super cute,” the source says, adding that when the dessert was wheeled out, “Lauren immediately called for Kyle to come over and stand next to her while she blew out her candles!”

But there WAS one small hitch in the icing on Lauren’s cake: apparently some of her party guests had slightly sticky fingers. “As the bash was winding down, people were leaving and trying to take bottles of liquor with them. Let’s just say some were successful and some weren’t!” chuckles our insider.

Regardless of guests helping themselves to their own personal bottle service, LC, your party sounds pretty awesome. What? Did our invite get lost in the mail?